The knives were sourced from the police. In total, around 2 tonnes of steel was melted.

"We wanted to create a space that would allow people to have more confidence in their bodies, so they wouldn't necessarily feel like they would need a weapon on the streets," Steel Warriors cofounder Ben Wintour told Business Insider.

The charity is partnering with trainers who have experience with knife crime as role models for youths.

Business Insider met with Derrick Twum who grew up in New York in a gang environment and served 14 years in prison because of knife crime.

Exercise helped him turn his life around and he now runs a fitness club in London, M.E.M. Fitness.

"Fitness changed my life. It's almost like therapy for me," he said. "It transformed my body, my thinking and now my business is all related to fitness. It wasn't just the cosmetic aspect of it, basically."

The gym is located at Langdon Park in Poplar. Steel Warriors hopes to expand the initiative and build other gyms like this across London.